Trabeculectomy is the most effective method of lowering intraocular pressure in glaucoma that is not well controlled with drop medication. The post-operative wound healing response remains the major barrier in surgical success. Scar tissue formation results in occlusion of the surgical drainage site created. As a consequence, the intraocular pressure rises once again. The current use of anti-scarring agents such as 5 Fluorouracil (5FU), is a well established method employed by ophthalmologists to clinically reduce the postoperative scarring response. However, in patients with a high risk of bleb failure, repeated subconjunctival injections of 5FU following bleb needling is often required resulting in increased clinical load and patient inconvenience. A slow release formulation of 5FU would be of benefit by releasing the 5FU into the subconjunctival space over an extended period thereby providing a prolonged therapeutic effect. In addition, hyaluronic acid is known to possess antifibrotic properties and from its gel-like physical state, would potentially act as a physical tissue spacer that may further limit active subconjunctival scarring at the site where it is injected. We hypothesise that injecting a mixture of 5FU with hyaluronic acid would give better outcomes than injecting 5FU alone.